Writing in The Guardian, Sir Bernard, who has just been offered a one-year contract extension, said "public confidence has been affected" by the Met's handling of inquiries into Lord Bramall and other high-profile figures.

The way officers investigate historical sex claims involving public figures would be part of the review, Sir Bernard added, suggesting a shake-up of policy to make it "more neutral".

Video:Met Chief Orders Child Abuse Review

He said current guidance from the HM Inspectorate of Constabulary stipulates that the victim should always be believed.

Sir Bernard said: "The public should be clear that officers do not believe unconditionally what anyone tells them. They are listened to, sometimes at length, before the decision is made to begin an investigation.

"A good investigator would test the accuracy of the allegations and the evidence with an open mind, supporting the complainant through the process.

"This is a more neutral way to begin than saying we should believe victims, and better describes our impartial mindset."

On Wednesday Sir Bernard again refused to apologise to Lord Bramall, 92, amid fierce criticism over Operation Midland, which saw officers raid the former Army chief's home.